Can't back up my MacBook to Sandisk Extreme

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Level 1

15 points

Can't back up my MacBook to Sandisk Extreme

I got a new MacBook Air about a month ago, and was trying to back it up to the Sandisk Extreme hard drive I used with my old MacBook. I erased and reformatted it, and it still tells me "Try backing up again when "Extreme SSD" is available." I found this in another discussion, changed the USB-C cable to an Apple one, restarted, and it still gives me the same message.

MacBook Air 13″, macOS 26.0

Posted on Nov 4, 2025 6:34 AM

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Answer 1

Tesserax

Level 10

157,860 points

Nov 4, 2025 8:13 AM in response to NineMuses

Four questions, if you don't mind:

By "backup, are you referring to using Time Machine or some other method?
Which exact model is your Sandisk Extreme?
What is the format of the Extreme: APFS or HFS+, or something else?
Is your "new" MacBook air the 2024 M3 or 2025 M4 model?

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Answer 2

NineMuses Author

Level 1

15 points

Nov 4, 2025 4:19 PM in response to Tesserax

Here are the answers to your question:

Backup using Time Machine.
SanDisk Extreme Portable SSD
I think the format is APFS. I think that's what I formatted it in. Is there someplace I can check for that?
2025 M4 model running Tahoe

I've had the SanDisk for a while, and had been backing up my old MacBook, so wanted to erase and reformat. It was working fine until I did that.

Thanks so much for any help you can provide.

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